The bill, if passed, could effectively mean kill switches on phones sold across the U.S.

Kill-switch technology that can render a lost or stolen smartphone useless would become mandatory in California under a new bill that will be proposed to the state legislature in January.

The bill will be introduced by Senator Mark Leno, a Democrat representing San Francisco and neighboring towns, and George Gascón, the district attorney for San Francisco. Gascón has been spearheading a push by major law-enforcement agencies across the U.S. for more to be done to prevent smartphone theft.

The proposed law could reach well beyond the borders of California. Because of the difficulty and added cost of producing handsets solely for sale in California, it could serve to make kill-switch technology a standard feature on phones sold across the U.S.

The snatching of smartphones, often at knife or gunpoint, has become one of the biggest types of street crime across the country. It accounts for around half of all street crime in San Francisco, according to Gascón's office.

Gascón and Eric Schneiderman, the state attorney general for New York, are at the head of a campaign to get phone makers and carriers to do more to make stolen cellphones useless.

Kill-switches typically work by wiping a phone of personal information and making it impossible to reactivate or reprogram without a passcode or other authorization. In theory, that should sharply reduce the incentive to steal phones because the handsets would become useless.

Two companies, Apple and Samsung, have already introduced such technology after hearing from Gascón and Schneiderman. Apple's activation lock is part of the new iOS7 operating system and Samsung preinstalls the Lojack for Android app, but that requires an annual subscription.

But Microsoft and Google, which were also contacted and asked to do more, have been dragging their feet.

A recent survey undertaken by Gascón's office found around four in five iPhone users were using the activation lock, but that's still a problem, he said earlier this week.

"Until Activation Lock is fully opt-out, it appears many iPhone owners will not have the solution enabled," he said in a statement. "This leaves iPhone users at risk, as thieves cannot distinguish between those devices that have the feature enabled and those that do not."

The bill would address that and will be formally introduced in January at the start of the 2014 California state legislative session.